The invention relates to an intraocular lens and in particular to an intraocular lens in which the focus can be adjusted after implantation. The invention also relates to a method for production of such a lens.
In patients affected by grey cataract, for example, it is at present customary to remove the diseased and opaque crystalline lens and to replace it with an implant, a so-called intraocular lens (IOL).
An example of an intraocular lens of this type is shown in FIGS. 1 and 2. The lens consists of a lens body 1 and of two haptic arms 3 connected to the lens body 1. FIG. 2 shows a side view of the lens from FIG. 1.
The lens is preferably made of a soft or foldable material so that it can be folded or rolled along the broken line (Axe2x80x94A). For implantation, after the diseased crystalline lens has been removed, the intraocular lens is inserted into the eye by being folded together during the insertion along the broken line so that the incision in the cornea can be made as small as possible. The lens is unfolded within the eye and is secured in its position, usually in the capsule of the removed lens.
The lenses, which are usually made of a synthetic material such as polyurethane elastomer, silicone elastomer, hydrogel polymer or collagen, can be formed in one piece and are therefore economical to produce. As they can be rolled up or folded up, they can be inserted through a small slit, with the result that the eye rapidly heals after the operation.
However, a disadvantage of these lenses is that incorrect fitting can easily occur, with the result that, even after the operation, the patient requires a means for correcting vision, for example glasses or contact lenses, because the focus of the lens lies before or behind the retina.
To rectify this problem, an adjustable intraocular lens has been proposed in U.S. Pat. No. 5,800,533 and in U.S. Pat. No. 5,728,155. Such a lens is shown in FIG. 3. This prior art lens consists of a cylindrical lens body 1 with an external thread 5, a support device 7 which is annular and has an internal thread 9 matching the external thread 5 of the lens body 1, and haptic arms 3 which are secured to the support device or are formed in one piece with the latter. As the lens body is screwed to a greater or lesser extent into the support device, the distance between the lens body and the retina, and thus the focus, is adjusted.
U.S. Pat. No. 5,728,155 also shows that a flexible lens body can be fitted into the support device, so that it is possible subsequently to exchange the lens via a small incision made through the cornea. This publication additionally discloses that the lens body can also be moved relative to the support device by means other than an internal thread and an external thread. For example, the lens can be moved using a worm gear secured on the support device.
However, these adjustable intraocular lenses have a number of disadvantages. On the one hand, they are difficult to produce because they are made up of several parts which have to fit each other with very tight tolerances. In particular, movement mechanisms using worm gears and the like are elaborate, complicated and expensive to produce.
A further disadvantage is that the lens body is held in an annular support device. The latter is usually rigid, so that a large incision is needed for implantation. Moreover, the support device reaches close to the field of vision of the patient, with the result that undesired reflexes and disturbances can be caused by the thick support device.
Further adjustable intraocular lenses are known from U.S. Pat. No. 5,203,788 and from U.S. Pat. No. 5,288,293. In particular, U.S. Pat. No. 5,288,293 discloses an intraocular lens in which the angle between the haptic arms and the lens body can be adjusted by an adjustment means, so that the lens body can be moved relative to the haptic arms in the direction of the optic axis. The adjustment means is a material formed at the juncture between the haptic and which connect to the implant lens. This material may be more readily subjectable to hydration, or in other cases to dehydration, such as the type of hydrogel or colagene. Thus, modifying the hapticoptic angle through laser energy treatment provides for an effect in the change of implant power. However, this kind of adjustment is not very precise and can be done only once. The adjustment is not reversible. Furthermore, the material placed at the boarder of the implant lens may cause undesired optical disturbance.
The object of the invention is to make available an adjustable intraocular lens which is easy and inexpensive to produce and which avoids the stated disadvantages.
This object is achieved by means of an adjustable intraocular lens and by means of a method for its production.
According to a further advantageous aspect of the invention, the whole lens can be folded or rolled so that it can be inserted through a small incision in the cornea.
In a particularly advantageous embodiment, the lens body and the haptic arms are made in one piece in one casting procedure.
According to a further advantageous embodiment of the invention, the adjustment means is a commercially available screw which can be re-adjusted after implantation, either by means of a very small incision through the cornea and engagement of an instrument in the screw, or non-invasively using a magnetic screwdriver.
A further aspect of the invention provides for the lens being adjusted by means of an electric motor, for example a piezoelectric element.
An advantage of the invention lies in the provision of an adjustable intraocular lens having an adjustment mechanism which does not cause optical disturbance.
A further advantage of the present invention lies in the fact that the adjustable intraocular lens can be adjusted repeatedly and reversibly.